The deep-freeze temperatures would be bad enough on those extremities the thermometer is not likely to top 25 degrees with lows in the single digits today but high winds will make it feel like 25 to 35 degrees below zero.

"Twenty below generally is the criteria for potential health danger," says Fred Davis, chief meteorologist for the National Weather Service at Baltimore-Washington International Airport. "The windchill applies to skin exposure. The best thing in these kinds of temperatures is to avoid long periods of exposure."

In the optimum situation, that would mean staying warm by staying inside. But when there is no choice, Dr. Tso says using some common sense can prevent frostbite and worst, hypothermia.

"A lot of body heat is lost through the head," she says. "Wearing a hat is very important. The nose is vulnerable. Wear a scarf. Cover your ears. Mittens are better than gloves because the fingers can touch and provide more body heat. You should wear several pairs of socks and waterproof shoes."

That takes care of the extremities. For the rest of the body, Dr. Tso recommends thermal underwear and layers of clothing rather than depending on just one heavy coat; a couple of thin sweaters, rather than one thick one.

"Layers trap heat and you get more insulation," she says.

If you have to be outside, you should be aware of danger signs.

"When you get pins and needles feelings or numbness in your fingers and toes and experience slowness of thinking, get out of the cold," Dr. Tso says. "If you can't get inside, try to get out of the wind."

Once you're thawed out, don't go back outside and "get refrozen," the physician says. "Frostbite damage to tissue and blood vessels is much worse then."

Dr. Tso says extended periods of cold will increase cold-related problems treated by the hospital, especially with groups like the homeless, alcoholics and the elderly.

When cold victims come in, she says, "We don't do anything dramatic in the emergency room unless the body temperature is below 90 degrees. Above that, we use blankets and light bulbs for warmth. The lowest body temperature I ever dealt with and the person survived was 86. We had to use a heart and lung machine normally used in heart bypass surgery. He recovered with no permanent damage."